Automatic steering system



Jan. 25,v 1944. B CHANCE 2,340,174

AUTOMATIC STEERING SYSTEM Filed Jan. 18, 1940 3 Sheets-Sheet l AUTOMATIC STEERING SYSTEM Filed Jan 18, 1940 3 Sheets-Sheet 2 Z as @Mays mx/007% Jam 25, 1944. B. CHANCE 2,340,174

AUTOMATIC STEERING SYSTEM Filed Jan. 18, 1940 3 Sheets-Sheet I5 Patented Jan. 25, 1944 AUTOMATIC STEERING SYSTEM Britton Chance, Mantolokinz, N. J.

Application January 18, 1940, Serial No. 314,558 In Great Britain January 19, 1939 'l Claims.

This invention relates to automatic steering gear for dirigible craft having rudders. In the conventional automatic steering system, it is necessary to apply follow-up or normal rudder which is proportional to the deviation of the craft from its course, and in order to steer accurately, especially in heavy weather, it is necessary to apply additional rudder at or near the peak of the crafts yaw, which is known as "initial rudder. The latter acts to` oppose the following yaw and is applied in anticipation of the same. The object of this invention is to provide an improved steering system embodying a no vel method and means for controlling rudder application by the utilization of what I choose to term inverse rudder." At least a portion of the latter is negative with respect to initial rudder and subtracts from the same. 'This inverse or negative rudder is applied as the next yaw peak is approached to reduce the amount of initial rudder. For convenience, the terms initial rudder and inverse rudder will be used throughout this specification. It will be understood, however, that these terms do not refer to separate rudder movements, but to components which are combined, andthe resultant of which is applied to the rudder.

It is well known that, for a variety of reasons, such as adverse weather conditions, size and shape of the craft, method of propulsion and quality of the steering gear, a craft constantlyrtends to deviate from its set course. This tendency may be counteracted by manual steering, the helmsman relying upon his experience to time the application of rudder; if the application of rudder is incorrectly timed for the existing conditions, then the deviation, or yaw, may become permanent. In countering the tendency to yaw by automatic steering gear, diiferent considerations apply. It is found that the steering is most satisfactory if a large portion of the full rudder angle required is made at the peak of a yaw and in such a sense that it will act to oppose the following yaw of the craft; for on account of the large inertia, especially of a sizable craft, the craft will swing past the set course towardsr a peak on the other side of the set course. It has been usual in the past to change the application of the rudder abruptly when the peak of the yaw is reached by moving the rudder back toor beyond' its central position in anticipation that the craft wil1 swing beyond its course.

I have found that a far better control is obtained by applying a very large amount of rudder at or near the peak of a yaw in a sense to oppose the yaw of the craft to the other side of 55 In Fig. 1 there is representedV schematically a the set course. as is customary, and then removing some of this initial rudder before the peak of the next yaw is reached. If the steering gear is of low sensitivity, the application of initial rudder may not take effect until a fraction of the yawing cycle after the peak of a yaw. In this manner. the rudder is held in a position such that a large torque is produced aiding the next yaw of the craft. If, however, this amount of rudder is reduced in the manner to be described, the effect of the torque in phase with the yaw is avoided.

According to the invention, the reduction of the amount of initial rudder is attained by use of inverse rudder. The application of initial rudder is a known expedient and need not be elaborated here; if means are provided in automatic steering gearfor applying initial rudder at the peak of a yaw, then according to the invention. a control will be provided to operate on the rudder, either directly or indirectly, this control being arranged to respond to displacement of the craft from its course and to give a predetermined amount of rudder depending upon the direction of deviation of the craft from its course. This control will be arranged to operate the rudder in such a sense as apparently to cause an increase of the yaw of the craft, thus applying what I have termed inverse rudder."

The invention may be clearly understood by reference to the accompanying drawings, wherein Fig. 1 is a schematic illustration of an apparatus embodying the invention;

Fig. 2 illustrates one form of inverse rudder device which may be employed;

Fig. 3 is a side elevational view of the same;

Fig. 4 is a detail sectional view along line 4-4 rudder effects are neglected. In any case. the

follow-up will give but small amounts of rudder for a given deviation of the craft from its set course and this effect will be more or less to provide a high damping factor for unusual yaws and for the usual course changing motions, and would not alter the principles involved here.

conventional automatic steering system I adapted to give initial rudder action. This device may take any known form, for example, it may be a device such as shown in my prior Patent No. 2,182,717, granted December 5,1939. There is also represented schematically an inverse rudder device 2 .provided according to the present invention. A specific form of this device is illustrated in Fig.`2

and will be described presently. The effects of the two devices I and 2 are combined in a conventional diiferential gea;` 3 and applied to the rudder to, give various rudder actions as described hereinafter.

In Figs. 2 to 5 there is illustrated one form of apparatus which may .be employed as the device 2 in Fig. 1 to provide inverse rudder according to the invention. A' support 4 carries a rotatable shaft (see Fig. 5) on which ismounted an arm 6. The supporting structure 4 also provides bearings 'I and 8 which' support rotatably adjustable arms 9 and I0, at the upper ends of vwhich are mounted arcuate contact members II and I2. The arms 9 and II) are formed of insulating material for a reason which will presently appear.

The contact members II and I2 embrace an insulating gear sector I3 (see Fig. 4), and are adjustable therealong by means of set screws I4 and I5. The gear sector meshes with pinion I6 whose shaft I1 is journaled in support 4 and is rotatable manually, by means of a control knob or the like, to shift the gear sector and associated contact members in either direction.

The arm 6 is rotatable, through a variable arc according to the yaw ofthe craft, by a compass repeater of known form represented schem-atically at I8. The drive for arm 6 is such as to permit a slipping action when the arm engages either of the adjustable stops I9 and 20 carried by arms 9 and I0. In the specific illustration, the drive for arm 6 comprises pulleys 2l and 22 and belt 23.

The arm 6 is bifurcated at its end and carries resiliently a contact roller 24 whose trunnions 25 are disposed inslots 26 in cooperative relation with springs 21. 'Ihe roller 24 rides over the contact members Il and I2 and thus selectively energizes windings '28 and 29 of a double acting relay whose pivoted armature 3| `selectively controls the circuits of the multi-held reversible motor 32. Thus, the relay contacts 33 and 34 are arranged tov control selectively the circuits of..

the motor ileld windings 35 and' 36,l Limit.

y switches 31 and 3,8,fcontrol`th`e extent yoif motorv operation in either direction,'thereby controlling the magnitude of the'inverserudder laction as exv` .ential gear of Fig. 1.

The operation of the inverse rudder device may be understood by considering a complete yawing cycle of the craft, as represented in Fig. 7, by the sinusoidal curve. The peak yaws in opposite directions are designated A and B respectively. The set course of the craft is represented by the axial line S. Now bymeans of the device of Fig. 2, inverse rudder may be applied at diilerent points in the yawing cycle and may be caused to assume various phase relations with respect to the crafts ya'w and the initial rudder. To explain this more clearly, there are represented in Fig. 6 various operating conditions of theinverse rudder device with respect to the yaw peaks A and u sultant rudder` application. For simplicity, it is B. In these representations, A and B again represent the yaw peaks, while CD represents the insulating section between.A the contact members II and I2. i

In operation, the trolley arm 6, is operated back and forth through an arc by the gyro compass I8'in correspondence to the crafts yaw, as will'be well understood. It will be seen that by means of the pinion I6, the operating cycle of the device may be shifted with respect to the yawing' cycle.

Assuming a given setting of. the pinion I6, let us suppose rst the case of Fig. 6 (a) where the insulating section CD is substantially a minimum in width, and the stops I9 and 20 are outside the range of. movement AB. With reference to Fig. '7, during the motion of the craft from yaw peak A to yaw peak B, the roller 24 reaches point D, thereby energizing the inverse rudder Vmotor, as shown in Fig. 2, and applying inverse rudder at a certain point in the yawing cycle as indicated at D1 in Fig. 7. The arrow indicates the direction of the inverse rudder. When the limit switch 38 opens, the motor is deenergized. The crafts yaw proceeds to the peak B, the roller -24 moving over contactvll. During the motion of the craft from yaw peak B to the next yaw peak A, the roller reaches point C, thereby energizing the motor to apply inverse rudder in the opposite direction at a point C1 (Fig. 7).

Let us assume now the case of Fig. 6 (b) where the insulating section CD is of considerable width. In this instance, inverse rudder is applied in one direction at point D2 and in the other direction at C2 (see Fig. 7)

In the case of Fig. 6 (c) the insulating section is substantially a minimum in width and the stops I9 and 20 are within the yaw peaks, as indicated. In this instance, the arm 6 will be against stop 20 at the time of yaw peak A, and when the yaw reverses the arm will start back immediately and the roller 24 will reach point D at a point Ds in the yawing cycle (see Fig. 7). Consequently, inverse rudder will be applied at that point, as indicated. The arm 6 will strike stop I9 at point Sb in the cycle and the belt 23 will slip while the yaw proceeds to peak B. Immediately upon reversal of the yaw, the arm 6 will move toward A and roller 24 will reach point C at point Ca in the cycle, thereby applying inverse rudder in the opposite direction. At point Se the arm 6 willstrike stop 20 and remain there while the yaw proceeds to peak A.

Thus,.it will be seen that inverse rudder may be variously applied by various adjustments of the apparatus. While only three conditions of the apparatus have been illustrated, it is possible by various combinations of the adjustments to ob.- tain a large number ofinverse rudder applications in relation to various initial rudder applications as depicted in Figs. 8 to 13 now to be described. These iigures show both initial rudder effects and inverse rudder effects obtainable in the 'complete apparatus shown schematically in l Fig. 1. They also show the resultant or useful assumed that the craft-'yaws at constant amplitude.

In Fig. 8, the initial rudder is shown to be' applied at the peak of a yaw and in a sense to oppose the motion of the craft on the following yaw. The inverse rudder is applied at the moment the craft swings across the set course. n The amount of inverse rudder applied is substantially the same as the amount of initial rudder. The lowerapart of Fig. 8 shows that the rudder is brought to a central position as the craft swings over the set course in anticipation of the crafts swinging on to the other side of the set course.

In Fig. 9, the apparatus for applying-initial rudder is represented as being of low sensitivity, the application lagging behind the peak yaw. The

inverse rudder application is, however, timed as in the case of Fig. 8 to take effect as the craft swings over the set course. The result is that the useful rudder is effective for a shorter period.

This principle is especially useful when the accuracy of the steering gear does not permit of the application of initial rudder until after the peak of a yaw has been reached; or there may be a time lag in the operation of the rudder motor. Under these conditions the initial rudder is maintained past the peak of the yaw, in which case the crafts heading and the rudder torque are in the same sense-a condition to be avoided if possible. It may be avoided, as shown, by the application ofv inverse rudder which diminishes the initial rudder at any desired time before the next peak is reached. c

It will be noted that the application of inverse rudder in Figs. 8 and 9 corresponds substantially to that illustrated in Fig. 6 (a) anddescribed above.

If, as shown in Fig. 10, the initial rudder is sensitively applied, butthe inverse rudder application lags behind the swinging of the craft over the set course, the useful rudder is effective for a longer period than in the cases of Figs. 8 and 9.

It will be noted that the application of inverse rudder in Fig. 10 corresponds substantially to that of Fig. 6 (b) as described above.

In Fig. l1, there is illustrated the effect of low sensitivity in the apparatus for applying inverse rudder as weil as in the apparatus for applying initial rudder.

While I have illustrated in Figs. 8 to 1l the application of initial and inverse rudderin equal proportions, it may be found that better control can be obtained by applying inverse rudder which is a fraction of the amount of initial rudder. In Fig. l2 there is illustrated the case where there is low sensitivity throughout and the inverse rudder application is about one-quarter of the initial rudder application.

In Fig. 13, there is illustrated the case where the apparatus for applying initial rudder is highly sensitive and the inverse rudder is applied as illustrated in Fig. 6 (c) and described above.

From the above description it will be seen that the invention enables the application of large amounts of useful rudder, since the inverse rudder is combined with the initial rudder, and the time of occurrence duration and magnitude of the useful rudder may be readily controlled by adjustment of the inverse rudder device. Thus, the system is extremely flexible and greatly enhances the steering of the craft.

It will be understood, of course, that the invention is capable of various modications and I claim:

sinusoidal path, means for applying large movement to the crafts rudder substantially at the peak of each yaw in a direction to oppose the next yaw, and means for subtracting at least a portion of said movement within each interim between Asuccessive applications of said rudder movement.

'2. In an automatic steering systemadapted to direct a dirigible craft along a substantially sinusoidal path, means responsive to the crafts .reaching substantially its peak yaw in either drection for throwing the crafts rudder in a direction to oppose the next yaw, and means responsive to the crafts yawing motion for subtracting at least a portion of therudder throw within each interim between successive rudder throws.

3. In an automatic steering system adapted to direct a dirigible craft along a substantially sinusoidal path, means responsive to the crafts reaching substantially its peak yaw in either direction for throwing the crafts rudder in a direction to oppose tne next yaw, means responsive tothe crafts yawing motion for subtracting at least a, portion or' the rudder throw within each interim between successive rudder throws, and means'for varying the operation of said lastnamed means so as to vary the time of occurrence and duration of its subtracting action.

4. In an automatic steering system adapted to direct a dirigible craft along a substantially sinusoidal lpath, means responsive to the crafts yawing motion for producing a mechanical movement which when applied to the crafts rudder imparts a relatively great throw thereto substantially 'at the peak of each yaw in a direction to oppose the next yaw, other means responsive to the crafts yawing motion for producing a mechanical movement having a predetermined relation to said iirst movement, and means for compounding said movements and for applying their resultant to the crafts rudder, the last-named movement serving to nullify at least a portion of the first-named movement to reduce the rudder throw between yaw peaks.

5. In an automatic steering system adapted to direct a dirigible craft along a substantially sinusoidal path, means responsive to the crafts yawing motion for producing a mechanical movement which when applied to the crafts rudder imparts a, relatively great throw thereto substantially at the peak of each yaw in a direction to oppose the next yaw, other means responsive to the crafts yawing motion for producing a mechanical movement having a predetermined relation to said rst movement, means for compounding said movements and for applying their resultant to the crafts rudder, the last-named movement adding to the first-named movement during a Ipart of the yawing cycle and subtracting therefrom during another part of the cycle,

and means forV varying the operation of said second means so as to vary the action of said last-named movement.

6. In an automatic steering system adapted to direct a dirigible craft along a substantially sinusoidal path, a first device adapted to produce a mechanical movement which when applied to the crafts rudder imparts a relatively great throw thereto substantially at the peak of each yaw in a direction to loppose the next yaw, a second device4 adapted to produce a mechanical movement having a predetermined relation to said rst movement, and means for compounding said movements and for applying their resultant to thel crafts rudder, the last-named movement serving to nullify at least a portion of the firstnamed movement to reduce the rudder throw between yaw fpeaks, said second device comprising a reversible motor, switching means for controlling the energzation of said motor, and means responsive to the crafts yawing motion for actuating said switching means. y

7. -In an automatic steering system adapted to direct a dirigible craft along a substantiallyrsinusoidal path, a, first device adapted to produce a mechanical movement which when applied to the crafts rudder imparts a. relatively great throw thereto substantially at the peak of each yaw in a direction to oppose the next yaw, a second device adapted to produce a mechanical move ment having a predetermined relation to said first movement, vand means for compounding said movements and for applying their resultant to the cratt's ruddemfthelast-named movement serving to nullii'y at least a `portion of the mst-named movement to reducethe rudder throw between yawpeakasaidasecond device comprising a reversible motor, switching means including spaced contact elements and a movable contact element, adjustable stops. for'said movable element, compass means, andl a slip drive-means interconnect- 'ing #said movableelement; and said compass means.

` BRI'I'ION CHANCE. 

